yellowcoupe

Hi there everybody,

*PS: this is a bit complicated so if u don't understand exactly what i'm writing, its ok, me too. I just want to get input from an expert if there are any out there*


ok so I wanted to know if anyone out there has done a thorough 4-wheel alignment for their cars (whatever model) and can discuss the results?

Specifically, what were the alignment specs BEFORE and AFTER the alignment and exactly how the driving charactieristics have changed.

As an illustration, my cars specs are below :


AFTER 1st alignment:
FRONT CAMBER ® -1 deg (L) -1 deg
FRONT TOE ® toe-out 5min (L) toe-out 5min
REAR CAMBER ® -1 deg (L) -1 deg
REAR TOE ® toe-out 5min (L) toe-out 5min

AFTER 2nd alignement:
FRONT CAMBER ® -1 deg (L) -1 deg
FRONT TOE ® toe-out 30min (L) toe-out 30min
REAR CAMBER ® -1 deg (L) -1 deg
REAR TOE ® toe-in 8min (L) toe-in 8min

Subjectively, I felt that after the 1st alignment, my turn-in was good but the rear seemed to swing out a bit too quickly. The funny thing is that the rear tyres didnt ssqueel very much even tho i felt the car's rear swinging out too fast under lift-off throttle conditions

After the 2nd alignment, I changed the settings.

Now the car handles very neutrally, breaking into more or less 4 wheel drift if i push hard (esp in the wet) Ok, so the turn-in seemed slightly less quick than before and the rear tyres squeal MUCH earlier and with much less provocation.

*whew... if you'd read this far congrats*

SO this part puzzles me and I wanna ask u guys out there abt it.

I thought that by changing my rear toe to a slight toe-in, there would be LESS oversteer (which is what i feel subjectively), BUT i don't understand why the rear tyres squeal so much now.

Doesn't a squeealing tire mean that I'm LOSING GRIP in the REAR WHEELS EARLIER THAN BEFORE and therefore mean I am actually OVERSTEERING MORE? If that is true, why do i paradoxically feel that the car handles better and oversteers LESS?

*double whew*

so if anybody knows what the hell i am talking about, please help me answer the question.

Much appreciated!

Mad-Machine

nope... if your rears are toed OUT, they are naturally trying to swing the rear around. In a hard corner, ignore the inside rear tire. It is not carrying that much weight and might be off of the ground. So it is only the outside rear that is holding up and controlling the rear of the car. If that tire is toed out, it is swinging ever so slightly wider than the fronts.. This is what makes the car more probe to oversteer.

By toeing them in, you are making those rear wheels want to try and make a SMALLER arc through the corner than the fronts.. this is understeer. The reason you are getting more squealing this way, by making the rear wheels work harder, they are rolling off of the tread and onto the sidewall earlier.

blue2000

based on what you've posted, I would expect less oversteer...and you confirm it. There's no reason to not believe it.

Squealing tires don't necessarily mean your losing grip but that is a slightly different discussion. Madmachine is right about the noise. The rear tire is trying to make a smaller arc thru the corner but it can't...though it is succeeding in holding the rear of your car "on line" (thus no oversteer). By adding toein, you forced the rear tires to "work harder"...and so there's more noise. But its the feel of the car that matters, not the noise. and by the way, different tires make different amounts of noise.

I've discovered a couple things getting my car set up for autocross. The primary lesson was...it doesn't matter what a book tells you or what some else tells you. If you make an adjustment to the car, and it drives better, then go with it. There is always more than one set up for a car and it depends on your basic driving style which is best FOR YOU.

I like my car to be a little loose in the rear, it suits my driving style to have it that way. If you see what I mean.

yellowcoupe

Tks to both Mad and Blue for the excellent replies!! mucho appreciated

I basically agree fully with BOTH of u and think that your explanations are correct.

I'm playing with my settings for tire pressure now and want to loosen up my rear just a bit more.

I am currently running 34psi all round. (that's when its cold... and goes up to 36psi all round when its driven hard)
I was thinking of increasing the rear to 35 or 36psi in an effort to possibly oversteer a very slightly bit more

any suggestions guys?

blue2000

The rear tires will heat up less, so you need to compensate for that a little.

Heres what I mean...I set my PSIs at 42 cold all around...knowing that the fronts will heat up more than the rears. More heat = higher PSI but also for the MX means more grip. So once my tires are "warmed up"... the fronts are at 45-6 PSI, and the rear is at 43-4. So I end up with the car handling the "best" after the tires warm up. If I set the tire PSIs when cold to get the handling I wanted on my first run (with cold tires)...by the 3rd run, I'd have A LOT of oversteer, instead of just a little...

If you see what I'm getting at?

yellowcoupe

whoah... 42 psi all round... thats very high isn't it?

The usual shops will inlfate only till 30psi as standard

I thought my 34 psi was going highish already

aren't u getting centre tire wear?

UltraTibby

I am running with 32 PSI rear and 38 PSI front and I havn't seen any noticable center wear.

blue2000

No I don't get uneven tire wear. At least not because of tire inflation.
My Kuhmo MX has a max cold psi of 51. 42psi is what I run on the street too.
My Perrellis on my other wheels also have a max cold psi of 51, but the like 38 psi for street driving.
My stock Michellins had a max cold psi of 44. I typically had them at 33 psi cold.
My 4Runner has big ol' off-road tires with a max cold PSI of 35...I inflate them to 28 on the road...and as low as 20 offroad.

My point is, every brand/model of tire is a little different. Go by what the tire sidewall says, not the cars ID plate. For street driving 75% of max psi is a good compromise for tirewear/fuel milage.

yellowcoupe

Blue,

have you ever used Yokohama Advan Neova AD07? or Bridgestone G3?
How does the MX compare with these or other tyres u have driven?

Was thinking of the MX

blue2000

No, I havn't had either of those tires. The MX is a very good tire; better than most other car tires I've had. You don't know me very well but the fact that I would buy them again says something.